In order to identify a user to a computer system, voice recognition software may be used. A user may speak one or more forms of identification to the voice recognition software, and the voice recognition software attempts to identify the user using what was said to the voice recognition software. The system also attempts to validate the identification using unique characteristics of the user's voice that have previously been identified during a “enrollment” procedure. The enrollment procedure enrolls the unique characteristics of the person's voice at a time when the person has been positively identified using means other than voice, such as visual identification or a PIN number.
One approach described in U.S. Pat. No. 5,517,558 issued to Schalk is illustrative. A user speaks, one character at a time, a password in response to a prompt. The password must be spoken one character at a time because single character recognition can be more accurate than whole word recognition for reasons such as the limited number of single characters. The system uses speaker-independent voice recognition techniques to recognize the characters spoken as a password. During this identification process, the system also extracts parameters from the password spoken that identify the unique details of the user's voice. These parameters extracted during the identification process are matched against parameters previously extracted during an enrollment process for the user having the password recognized.
If the two sets of parameters match relatively closely, there is a high probability that the user is the user identified. If the two sets of parameters have little in common, the user may be rejected, and if the two parameters are in between a close match and little in common, Schalk prompts for additional information, also to be spoken one character at a time. Speaker independent techniques are used to recognize the additional information, and a match is attempted against additional information stored for the user to validate the identity of the user. However, in the preferred embodiment, Schalk always prompts the user for the additional string and uses speaker independent voice recognition techniques to confirm the identity of the individual by matching the second string to corresponding information stored for the user.
There are several problems with this approach. First, each password in the system must be unique because the password is used to uniquely locate the characteristics of the person's voice. To enforce the rule that all passwords are unique, passwords must be assigned rather than chosen, or some users will not get their first password choice and must select another password. In such systems, users who cannot use their first choice as a password tend to forget their passwords more often than a system in which every user can use their own first choice password, even if such password is already being used by another user. Second, the Schalk system requires passwords to be spoken one character at a time. Users may find such a system unnatural to use.
What is needed is a method and apparatus that can identify a user without requiring that all passwords be unique or spoken one character at a time.